In recent years, a communication method called Bluetooth® communication has attracted an attention as a close range wireless communication method up to approximately 100 m at maximum and various kinds of supporting device have been developed.
A close range wireless communication system such as the Bluetooth® communication which uses a wireless signal of a comparatively high frequency wave has an advantage such as no directivity and high transmissivity in comparison to an infrared data communication method which uses an infrared signal, and is expected that devices supporting the system increase in the future.
In a communication system to which the infrared data communication method is applied, in order to establish a connection for the communication it has been necessary to specify a device to establish communication with a light emitting portion of a device and a light receiving portion of another device, which are mutually a connection target, opposing to each other. Further, it has been necessary to maintain a position at a time of the connection during the communication due to its directivity. On the other hand, in the communication system using a high frequency signal such as the Bluetooth® communication, such restriction on the position becomes not necessary.
When the Bluetooth® communication is used, an inquiry message is transmitted as a broadcast message from a device which intends to start communication (hereinafter, referred to as a device A) in order to discover devices which exist in the neighborhood thereof. Then, a device which has received the inquiry message from the device A sends back a response message to the device A in response to that inquiry message. By receiving the response messages sequentially from respective devices which exist in the neighborhood, the device A can discover a plurality of communicable devices which exist in the neighborhood. In accordance with information of those response messages, the device A selects and specifies a device to which the connection is tried, and connection processing with respect to the device is performed. On this occasion, when the response messages are received from a plurality of devices, conventionally those are displayed in a form of list so that a user can make a selection.
In the Bluetooth® communication, not only a communication path is established, but also what kind of application and service is implemented in the communication path is defined clearly as a profile. As the profile, there are a serial port profile to perform serial communication, a personal area networking profile to realize a personal area network and the like. A service discovery protocol (hereinafter, referred to as a SDP) is defined as a procedure to determine those profiles and a service which is actually implemented.
The device A transmits to a device to be connected (hereinafter, referred to as a device B) an inquiry message querying what kind of service is provided by the device B in accordance with the SDP, the device B receives the inquiry message from the device A and then transmits to the device A information regarding a service provided by the device B as a response message to the inquiry. If the device B provides a desired service, the device A having received the response message requests the communication for the service, so that the desired service can be started between the device A and the device B.
As described above, a basic communication procedure in the Bluetooth® communication is that first the device A performs transmission of an inquiry message in order to discover a device which exists in the neighborhood and also performs reception of a response message thereto; selects a desired device from devices which have responded; further, makes an inquiry to the device whether the desired service is available; and furthermore, requests the communication for that service.
The Bluetooth® standard is managed by Bluetooth SIG Inc. and specifications describing the details are published by Bluetooth SIG Inc.
Meanwhile, in a close range wireless communication system such as the Bluetooth® communication, an inquiry message to discover a device which exists in the neighborhood is targeted at all devices which exist within a communicable range (for example, from 10 m to 100 m). Accordingly, when many communicable devices exist in the neighborhood, enormous number of response messages are to be received. Conventionally, such an operation procedure of showing information regarding a device included in those response messages in a display or the like is required so that a user can select the desired device; however, when many devices exist in the neighborhood, the user must spend a huge amount of time for the selection operation and its usability becomes deteriorated, which has been a problem. Further, in order to judge whether the device is really a target device to connect or not, information such as an ID which is provided by the device needs to be identified, and therefore, there has been a possibility for the user to make an excessive operation.
In order to solve the above problem, a method of efficiently performing a procedure to discover a device to be connected by altering a reaching range of an inquiry message has been proposed in Japanese Published Patent Application No. 2001-144781, for example. According to the method, it is possible to efficiently specify the device to be connected by restricting a searching range of devices to a close range, for example, so that the number of devices to be discovered is limited.
However, when many devices exist within the close range, the same problem as before still occurs, and therefore, such a procedure of selecting a specific device from a list by the user is required, for example. This problem still remains when considering that each device existing around us will be supported by a network in the future. Further, in this method, an attention is paid to easily discovering a device to be connected, and a subsequent operation such as a selecting procedure of a service to be started cannot be simplified.
The present invention is made in view of such circumstances, and aims to perform easily and securely a communication service between devices when performing wireless communication which is represented by the Bluetooth® communication.